This specification relates to information presentation.
Sponsored content (e.g. advertisements, deals or special offers) can be provided over the Internet to various user devices. For example, a web page can include slots in which sponsored content can be presented. These slots can be defined in the web page or defined for presentation with a web page, for example, along with search results or other content. Sponsored content can also be delivered through dedicated web portals or applications executing on the user devices.
Some content items are expandable. For example, a content item can be initially presented in an unexpanded form as a 728×90 pixel graphical item. When a user selects or interacts with this content item, an expanded view of 728×270 pixels can be presented. The expandable content items can be processed on the user device in several different ways. For example, the resource served by a publisher may be configured to render the expandable content item within the same frame of the resource. Alternatively, the resource served by a publisher may be configured to render the expandable content item within one or more nested iFrames of the resource.
To facilitate the processing of expandable content items in particular types of content item slots, such as in the case of iFrames, a content item provider (such as, in the case of advertisements, a vendor that serves advertisements for advertisers) provides a “publisher side file” (PSF) for a publisher host. The PSF file stores instructions that are used to ensure proper rendering, expansion and contraction of the expandable content item. Often the vendor specifies a location on the publisher host for storing the file so that a user device can request the publisher side file from the host. For example, a specified location for a particular vendor Vendor1 may specify a directory entitled “Vendor1Path” at the root of a publisher webserver. Thus, the publisher side file V1PSF.html for Vendor1 for a host www.example1.com may be retrieved by the URL:                http://www.example1.com/Vendor1Path/V1PSF.html.        
However, not all publishers may store a publisher side file for each specific vendor. For example, a particular publisher may never obtain a publisher side file, or the publisher may accidentally delete the publisher side file, or some other action or inaction may result in the publisher not having a publisher side file for a particular vendor. Thus, if the particular vendor serves an expandable content item for a particular content item environment that requires a publisher side file, and the publisher side file is not available at the publisher, the expandable content item will not be able to properly render.